1. Field of the Invention
The present invention relates to a method and device for clamping the electrode contact shoes around the electrode of an electric furnace, such as an electric arc furnace.
2. Description of Related Art
The electrodes of electric furnaces are customarily held by means of electrode contact shoes which grip around the electrode and are clamped against the electrode by means of mechanical devices or devices working by fluid.
In many cases the holder accordingly acts also as a contact shoe and thus transmits the electric current. In present practice the number of contact shoes around the electrode is relatively small. The device includes means for mounting at least one continuous pressure element and a plurality of closely spaced electrode contact shoes. This arrangement has been arrived at because the force clamping the contact shoes against the electrode is produced separately for each individual contact shoe.
The clamping force is produced, for example, with the aid of a rubber membrane which is fashioned to fit the contact shoe closely and to which insignificant pressure is applied.
Such rubber membranes, however, are costly to manufacture. Their maintenance and installation are troublesome because each one of them requires its own individual hydraulic unit but nevertheless it is not possible to replace one rubber membrane or contact shoe without dismantling the entire pressure ring system. It has not proved possible to seal the gaps between the contact shoes and consequently the hot furnace gases escape through these gaps so that there is an obvious danger of the rubber membranes becoming burnt. The contact area between the electrode and the contact shoes through which the current is supplied is often quite small compared with the available area, in other words only a line contact is achieved. As the number of contact shoes is small their size in the vertical direction must be correspondingly greater in order that even with only a line contact a sufficient flow of current to the electrode is achieved.